Bond Interaction Between Concrete Pavement and Lean Concrete Base

In the past, concrete pavement design procedures have been based on stresses computed with the assumption of either a frictionless or a fully bonded interface between pavement layers. It is recognized that neither of these assumptions is realistic for layers not intentionally bonded. Information on the degree of interaction between pavement layers is provided. Full-scale load-induced strain and falling weight deflectometer testing was conducted to measure the degree of bonding between portland cement concrete pavement and a lean concrete base (LCB) layer prepared using five commonly specified interface treatments. For each interface treatment, the effect of extending the LCB layer beyond the slab edge was also evaluated. Strain gauges installed at different pavement depths measured the load-induced edge and wheelpath stress profiles, which allowed the degree of layer interaction to be evaluated. By analysis of load-induced stress and deflection, it was verified that a double layer of polyethylene promotes an unbonded interface with very little frictional interaction. Other interface treatments create varying degrees of friction or partial bond between the layers, reducing the loadinduced stress. Slab bottom tensile stress reductions were computed in comparison with measured slab top compressive stress, measured polyethylene interface tensile stress, and theoretically calculated unbonded stress. Overall, the most effective stress-reducing interface treatments were asphalt emulsion and plain (no treatment) conditions, where tensile stress reductions of more than 40 percent were measured.